A capacitance type semiconductor dynamic quantity sensor is generally equipped with a beam-shaped movable electrode formed from a semiconductor, which is supported so as to be displaceable in a predetermined direction in accordance with an applied dynamic quantity relatively to a support substrate, and a beam-shaped fixed electrode formed from a semiconductor, which is fixedly supported on the support board and also disposed so that the side surface thereof faces the side surface of the movable electrode.
In the capacitance type semiconductor dynamic quantity sensor as described above, when the movable electrode is displaced in response to application of a dynamic quantity, the applied dynamic quantity is detected on the basis of variation in electrostatic capacitance between the side surface of the movable electrode and the side surface of the fixed electrode. Here, the dynamic quantity is acceleration, an angular velocity, pressure or the like.
Such a capacitance type semiconductor dynamic quantity sensor as described above has been proposed in, for example, JP-A-11-326365 hereinafter referred to as “Patent Document 1”). The acceleration sensor has such a comb-shaped structure that plural movable electrodes are disposed in a comb-shaped arrangement and also plural fixed electrodes are disposed in a comb-shaped arrangement so as to be respectively fitted in the gaps between the teeth of the comb-shaped arrangement of the movable electrodes
When a smaller dynamic quantity is required to be detected by the capacitance type semiconductor dynamic quantity sensor as described above, there may be used a method of increasing the length of the beam-shaped movable and fixed electrodes to increase the confronting area between these electrodes, so that the initial capacitance is increased and thus sensitivity is enhanced.
In the case of this method, however, the electrodes are weak in rigidity and sag because the electrode length is increased, so that a phenomenon that the movable and fixed electrodes are brought into contact with each other and become stuck to each other, referred to as sticking, is liable to occur. Such sticking causes operation failure of the sensor, etc., and thus it must be avoided.
There is henceforth increasingly required a sensor that can detect a smaller dynamic quantity with high sensitivity, and thus the movable and fixed electrodes are required to be increased in length.
However, in this case, the movable and fixed electrodes are more liable to sag, and thus sticking is more liable to occur.
Here, when the movable and fixed electrodes are increased in length, it may be simply considered that the rigidity of the electrodes could be enhanced by increasing the width of each of these electrodes. However, the increase in width of both the movable and fixed electrodes causes increase in size of the substrate area constituting the sensor. Therefore, this is not preferable.